The proposed work is centered in the development of a different class of fluorescence probes, based on electronic transitions sensitive to the polarity and viscosity of the microenvironment, to study membrane and enzyme models. Our research program is designed by the premise that the techniques developed for studying membrane models could be adapted to investigate biomembranes and enzymes. It is yet not understood how the physical properties of the bilayers affect the conformation, function and activation of proteins. Structural and dynamical information could be obtained studying perturbations of the fluorescence spectra of these fluorescent organic molecules, namely the red-shifting of the bands as function of polarity, emission decay times as well as depolarization of the emission, in complex fluids such as cationic, anionic, neutral and reversed micelles, and in more realistic membrane models such as vesicles. In order to develop new fluorescence probes based on charge-transfer transition for measuring micropolarity in membrane model systems, it should be calibrated the red-shift of the band as function of the polarity of the medium. Solvatochromic plots need to be constructed from aprotic, protic solvents such as alcohols, and water mixtures with polar solvents. Students will have the opportunity of learning several experimental techniques that would allow them to address a wide variety of biomedical problems. They will be encouraged to interact with other scientific groups through their participation in Regional and National Scientific Meetings and working for a few days in the Center of Fluorescence Spectroscopy at the University of Maryland.